This invention relates generally to electrically isolating a rail embedded in concrete, asphalt or paver construction, including shared right-of-way, dedicated right-of-way and at-grade crossings and more particularly to an elastomeric boot that partially encases such a rail.
Due to the expansive presence of railway systems, rail beds must often cross a roadway or a pedestrian walkway at grade level or be built within the same roadway. At such intersections, the recessed areas of the rail bed are often built up so that the surface of the road or walkway is at the same level as the top surface of the rails, with the exception of the recesses provided adjacent to the rails to accommodate the rail car wheels.
To accomplish this type of shared right-of-way construction, the recessed areas on either side of the rails are often filled with road material, such as asphalt, poured concrete, or precast concrete structures. However, because the rails are often used as signal conductors or negative returns for the railcar""s power traction and to inhibit the corrosion of the rails, they must be substantially electrically isolated from the ground. Further, it is beneficial to provide a flexible interface between the rail and the road material to allow for thermal expansion and contraction and mechanical loading and unloading of the rail itself. For this purpose, the rails are normally encased in some type of insulating material before the ground is filled with concrete or asphalt.
In some cases, a liquid settable elastomer is poured around the rails, such as disclosed in U.S. Pat. No. 4,449,666. However, this process can be very tedious and expensive. A more practical method of encasing the rails is to wrap them with a preformed elastomeric boot. Some examples of this method are shown in U.S. Pat. Nos. 4,641,779 and 5,464,152.
Existing designs for rail boots have proven to have some significant shortcomings. The soft, flexible nature of the elastomeric material is necessary for expansion, but is particularly susceptible to puncture damage by road traffic and by fasteners used to secure the rail at its base. Further, the boots may not bond particularly well to the surrounding road material and chasms may begin to open up at the interface. Additionally, when the rails are placed under a load by a train, the rails may flex and pull the boot away from the road surface. Moreover, even with preshaped boots, installation can be rather tedious, and may require that some type of tape or adhesive be used to secure the boot to the rail while the filling material is being poured or placed.
Elastomeric rail boots also serve to prevent the transfer of vibrations from the rails that can cause excessive noise and even damage the embedded track work or crossing structure. While existing designs tend to isolate the higher frequency vibrations, the solid elastomeric material tends to transfer the more pervasive low frequency vibrations to the surroundings.
The object of this invention is to provide a rail boot that can be used with a variety of different rail types in embedded track work that will maintain a close fit to both a rail and road materials during loading conditions.
The insulating rail boot encases a rail embedded in concrete, asphalt or paver construction, including, shared right-of-way, dedicated right-of-way and at-grade crossing. The rail and the rail boot are secured in place by retaining clips. The rail boot has two exposed top surfaces and a plurality of longitudinal cavities within the body of the boot. The top surfaces of the rail boot are sloped away from the rail. Top surfaces are designed to be a minimum of 1xe2x80x3 wide to provide necessary relief from the adjacent paved surfaces and reduce the incidence of stray current leakage. An outside edge of each top rail boot surface is positioned flush with a surface of the road material. This cooperation between the top surfaces of the rail boot and the road surface facilitates flow of water and debris away from the rail.
It is one important aspect of this invention to provide a rail boot that is resistant to puncture by pneumatic and solid tire traffic and by rail fasteners.
In accordance with another aspect of this invention, it is further desirable to provide a rail boot that will mitigate the transfer of high frequency vibrations from the rail.
These and other aspects of this invention are illustrated in the accompanying drawings, and are more fully disclosed in the following specification.